Isotherm ethylene

Now consider a solubility isotherm at T, slightly less than the UCEP temperature (figure 3.18d). At this temperature, solid-gas equilibria exist at all pressures, since the SLV line is never intersected. As the UCEP pressure is approached the gas phase becomes highly compressible, due to the influence of the vapor-liquid critical point, and the solubility of the solid in the gas phase begins to increase. As the pressure is increased in the immediate vicinity of the UCEP pressure, the T isotherm exhibits a large solubility enhancement. At pressures much higher than the UCEP pressure, the gas is less compressible, therefore the solubility of the solid quickly reaches a limiting value. This solid solubility behavior is similar to the 50°C naphthalene-ethylene isotherm. 

The highest power of the series terms chosen to define each isotherm reflected the extent of the nonideality. For the ethylene isotherms, a cubic series was used for temperatures from 0° to 25°C and a quadratic series was used for temperatures from 75° to 175°C. At 50°C, a quadratic series as well as a cubic series were used. For the helium isotherms, a quadratic series was used with the virial coefficient of the quadratic term treated as a constant obtained from published values rather than as a parameter. The other parameters were evaluated more accurately with the quadratic coefficient treated as a constant rather than as a parameter since the contribution of this term was so small for our range of pressures. The term functioned only as a virial remainder. In the helium data analyses, the parameters were common to all of the data. For the ethylene data analyses, only the virial coefficient parameters were common to all of the data an initial density parameter was required for each sequence... 

Many simple systems that could be expected to form ideal Hquid mixtures are reasonably predicted by extending pure-species adsorption equiUbrium data to a multicomponent equation. The potential theory has been extended to binary mixtures of several hydrocarbons on activated carbon by assuming an ideal mixture (99) and to hydrocarbons on activated carbon and carbon molecular sieves, and to O2 and N2 on 5A and lOX zeoHtes (100). Mixture isotherms predicted by lAST agree with experimental data for methane + ethane and for ethylene + CO2 on activated carbon, and for CO + O2 and for propane + propylene on siUca gel (36). A statistical thermodynamic model has been successfully appHed to equiUbrium isotherms of several nonpolar species on 5A zeoHte, to predict multicomponent sorption equiUbria from the Henry constants for the pure components (26). A set of equations that incorporate surface heterogeneity into the lAST model provides a means for predicting multicomponent equiUbria, but the agreement is only good up to 50% surface saturation (9). 

These equations hold if an Ignition Curve test consists of measuring conversion (X) as the unique function of temperature (T). This is done by a series of short, steady-state experiments at various temperature levels. Since this is done in a tubular, isothermal reactor at very low concentration of pollutant, the first order kinetic applies. In this case, results should be listed as pairs of corresponding X and T values. (The first order approximation was not needed in the previous ethylene oxide example, because reaction rates were measured directly as the total function of temperature, whereas all other concentrations changed with the temperature.) The example is from Appendix A, in Berty (1997). In the Ignition Curve measurement a graph is made to plot the temperature needed for the conversion achieved. 

The polymorphic behavior of PVDF has been found to be changed also in the presence of functionalized ethylene-propylene copolymers, for the case of samples isothermally crstallized from the melt [103]. 

The predominant gaseous products of the decomposition [1108] of copper maleate at 443—613 K and copper fumarate at 443—653 K were C02 and ethylene. The very rapid temperature rise resulting from laser heating [1108] is thought to result in simultaneous decarboxylation to form acetylene via the intermediate —CH=CH—. Preliminary isothermal measurements [487] for both these solid reactants (and including also copper malonate) found the occurrence of an initial acceleratory process, ascribed to a nucleation and growth reaction. Thereafter, there was a discontinuous diminution in rate (a 0.4), ascribed to the deposition of carbon at the active surfaces of growing copper nuclei. Bassi and Kalsi [1282] report that the isothermal decomposition of copper(II) adipate at 483—503 K obeyed the Prout—Tompkins equation [eqn. (9)] with E = 191 kJ mole-1. Studies of the isothermal decompositions of the copper(II) salts of benzoic, salicylic and malonic acids are also cited in this article. 

C.G. Vayenas, C.Georgakis, J. Michaels, and J. Tormo, The role of PtOx in the isothermal rate and oxygen activity oscillations of the Ethylene Oxidation on Pt, J. 

Sf.I f-Tfst 4.4B In a petroleum refinery a 750.-L container containing ethylene gas at 1.00 bar was compressed isothermally to 5.00 bar. What was the final volume of the container ... 

This parameter takes into account the presence of inerts, the use of nonstoichiometric quantities of reactants, and the presence of one or more of the reaction products in the original system. To illustrate this point, let us consider as an example the isothermal gas phase hydrogenation of ethylene (C2H4 + H2 - C2H6) taking... 

Ethylene adsorption at room temperature is rapid and reversible. Even after prolonged exposure to the catalyst, the ethylene is recoverable as such by brief evacuation (10). The isotherms are nonlinear and show some evidence of saturation at 0.5-0.6 cm3/gm, a value roughly five times that of the type I hydrogen. Since the adsorption is quite weak, it would seem that this adsorption is, in part, physical adsorption. To investigate this possibility, adsorption of ethylene (boiling point — 104°C) was compared to that of ethane (boiling point — 89°C) (IS). By traditional criteria physical adsorption of ethane should be greater than that of ethylene, and the comparison of the relative adsorption should let us assay what fraction of the ethylene adsorption is physical. 

The reaction is maintained at isothermal conditions. The effluent from the reactor is allowed to pass to a separatory vessel in which unconverted ethylene is removed for recycling. The molten polyethylene gets chilled below its crystalline Melting point. 

Step Transient Experiments at 800 Torr. Activation of pretreated silver was performed under isothermal conditions at 493, 523, and 543 K and 800 torr using a step transient format. A typical spectrum collected at 493 K, obtained by simultaneously pulsing ethylene-d4 and oxygen-18 from separate pulse valves into a continuous helium flow, is plotted in Figure 4. In this example, the oxygen to ethylene ratio was 2 1. As observed in the steady-flow TPSR experiments, the pretreated sample is readily activated, while the preoxidi samples remain inactive. 

The feed gas flow rate was monitored and controlled by mass flow controllers. Product gases were fed through heated stainless steel lines to a sample loop in an automated gas chromatograph. The GC analysis was performed using two isothermal columns (80°C) in series, a Porapak T and a Molecular Sieve 5A column. When necessary, a second GC analysis using a temperature programmed Hayesep R column was used to separate and detect small hydnx arbons (such as ethylene and ethane) and H2O. 

Fig. 5. Adsorption isotherms and composition of the gas phase for the adsorption of ethylene on (a) rhodium—silica and (b) palladium—silica at 20°C. o, Total molecules adsorbed , ethylene , ethane.

Fig. 6. Adsorption isotherms for 14C-ethylene and the effect of hydrogen on the adsorbed species for (a) nickel—alumina and (b) palladium—alumina at 20°C [63],...

Fig. 27. 14C-acetylene adsorption isotherm on palladium—silica at 20°C (O) and the 14C-ethylene adsorption isotherm on an acetylene-precovered palladium—silica catalyst... 

Fig. 95. Absorption isotherms of ethylene glycol dinitrate (from solution) by nitrocellulose of 12.2% N (Desmaroux [46]) as a function of concentration (a) and activity (b). Absorption of nitroglycerine (NG) is also given (b).

Prediction of the breakthrough performance of molecular sieve adsorption columns requires solution of the appropriate mass-transfer rate equation with boundary conditions imposed by the differential fluid phase mass balance. For systems which obey a Langmuir isotherm and for which the controlling resistance to mass transfer is macropore or zeolitic diffusion, the set of nonlinear equations must be solved numerically. Solutions have been obtained for saturation and regeneration of molecular sieve adsorption columns. Predicted breakthrough curves are compared with experimental data for sorption of ethane and ethylene on type A zeolite, and the model satisfactorily describes column performance. Under comparable conditions, column regeneration is slower than saturation. This is a consequence of non-linearities of the system and does not imply any difference in intrinsic rate constants. 

Figure 5 shows the experimental breakthrough curves obtained by Sheth (14) for saturation and regeneration of a 4A molecular sieve column with a feed stream containing a small concentration of ethylene in helium. The equilibrium isotherm for this system is highly nonlinear, and, as a result of this, the saturation and regeneration curves have quite different shapes. However, the theoretical curves calculated from the nonlinear analysis using the same values of the parameters bqB and D /rz2 for both... 

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